Ductal carcinoma in situ (DCIS) is the most common type of non-invasive breast cancer diagnosed in women and an immediate precursor to invasive ductal carcinoma (IDC). Current cyto- and histopathological approaches do not accurately predict disease progression, resulting in patients being under-treated or over-treated for DCIS. Our long-term goals are to identify key factors that lead to IDC that will enable the development of a molecular based approach to predict the risk of IDC, and a more tailored approach to treat DCIS. CCL2/CCR2 chemokine receptor signaling in DCIS is a potentially important mechanism for DCIS progression to IDC. CCR2 and its binding ligand CCL2, are overexpressed in breast ductal carcinomas, and correlate with tumor grade and poor patient prognosis. CCL2/CCR2 chemokine signaling is best known for regulating macrophage recruitment. However, knockdown of CCL2 significantly inhibits mammary tumor progression without significantly affecting macrophage recruitment. Overexpression of CCR2 in ductal carcinoma cells enhances cell survival and invasiveness, associated with increased expression of pro-survival and pro-invasive proteins (ALDH1A1) and decreased expression of pro-apoptotic proteins (Htra2). These studies indicate an important role for CCR2 signaling in breast ductal carcinoma progression. To clarify the in vivo role of CCL2/CCR2 signaling, we have developed novel xenograft models through mouse Mammary intraductal injection (MIND) of human breast carcinoma cell lines, Sum225 and DCIS.com. The Sum225 MIND model form stable non-invasive lesions, while DCIS lesions progress to IDC in the DCIS.com MIND model. Compared to conventional transplant models, these MIND models more closely mimic the biology of DCIS found in patients. Compared to Sum225 lesions, DCIS.com lesions show higher expression of CCL2, CCR2 and ALDH1A1 proteins and lower expression of Htra2, correlating with progression to invasive carcinoma. Based on preliminary studies, we hypothesize that CCL2/CCR2 signaling in ductal carcinoma cells enhances progression of DCIS to IDC. Aim 1: To characterize the role of autocrine CCL2/CCR2 signaling in ductal carcinoma cells during DCIS by analyzing effects of CCR2 overexpression and knockdown in MIND models, 3D cell culture models and biochemical approaches, using primary and established breast cancer cell lines. Aim 2: To determine the functional contribution of stromal derived CCL2 on CCR2 mediated progression of DCIS, by analyzing the effects of CCL2 derived from fibroblasts on DCIS progression, using subrenal graft transplant models, MIND models, 3D cell culture models and biochemical approaches, using primary and established breast cancer cell lines. Through a multiple PI plan, the objective is to determine how CCL2/CCR2 signaling regulates expression of pro-invasive and pro-survival factors (ALDH1A1) and pro-apoptotic factors (Htra2) to promote ductal carcinoma progression. These studies will reveal mechanistic insight into the role of chemokine receptor signaling in DCIS, with important therapeutic implications. .